X-ray Diffraction Measuring Device and Residual Stress Calculation Method Using the X-ray Diffraction Measuring Device

Abstract

To provide an X-ray diffraction measurement apparatus and a residual stress calculation method using the X-ray diffraction measurement apparatus that can correctly calculate the residual stress of a measurement object OB even when the imaging surface and the X-ray are not orthogonal. 【Solution means】 Detect the diffraction ring of a first sample with a known diffraction angle in advance, detect the diffraction ring of a second sample with a known diffraction angle and a different diffraction angle from the first sample in advance, obtain the centroid position coordinates of the first diffraction ring and the centroid position coordinates of the second diffraction ring, and from the centroid position coordinates of the diffraction ring of the first sample and the centroid position coordinates of the diffraction ring of the second sample, obtain the X-ray optical axis tilt, which is the tilt of the X-ray optical axis with respect to the imaging surface. Obtain the X-ray emission point coordinates of the imaging surface when the distances to the first sample and the second sample are set to zero, detect the diffraction ring of the measurement object based on the calculated X-ray optical axis tilt and the X-ray emission point coordinates of the imaging surface, and correct the centroid coordinates of the diffraction ring of the measurement object to calculate the residual stress of the measurement object.

Description

Technical Field

[0001] The present invention relates to an X-ray diffraction measurement apparatus that emits X-rays toward a target measurement object and calculates the residual stress of the measurement object, and a method for calculating residual stress using the X-ray diffraction measurement apparatus.

Background Art

[0002] Conventionally, an X-ray is irradiated onto a measurement object at a predetermined incident angle, and an X-ray diffraction ring (hereinafter referred to as a diffraction ring) is formed on an imaging surface by the X-ray diffracted by the measurement object. The shape of the formed diffraction ring is detected and analyzed by the cosα method, and an X-ray diffraction measurement apparatus for measuring the residual stress of the measurement object is known.

[0003] In this X-ray diffraction measurement apparatus, there is a device that uses an imaging plate as an imaging surface, images a diffraction ring on the imaging plate by irradiating the measurement object with X-rays, and then irradiates the imaging plate while scanning a laser beam to detect the emission intensity together with the scanning position, thereby detecting the shape of the imaged diffraction ring.

[0004] For example, the diffraction ring forming apparatus shown in Patent Document 1 includes an X-ray emitter for irradiating an X-ray onto a measurement object and a case incorporating an imaging plate for recording the diffraction ring. The case has a planar wall orthogonal to each other, parallel planar walls intersecting at an angle of approximately 45 degrees with the planar wall, and a planar wall perpendicular to the planar wall. The optical axis of the X-ray emitted from the X-ray emitter is included in a plane orthogonal to the planar walls, respectively, and is parallel to the planar walls, respectively. The X-ray emitter is arranged in the case at a position near the intersection line extending the planar wall so that the incident angle with respect to the planar wall becomes a predetermined angle.

[0005] In addition, in the X-ray diffractometer of Patent Document 2, when the mounting part is mounted on the rail, the X-ray diffractometer is installed on the rail, and the incident angle ψ0 of the X-ray is set to a single incident angle. The X-ray diffractometer is stopped at an arbitrary measurement position on the rail, and the X-ray generated by the X-ray generator is irradiated from the X-ray irradiation unit to the X-ray irradiation point on the top surface. As a result, the diffracted X-ray from the rail enters the imaging plate, and the entire image of the diffraction ring is captured and recorded by the imaging plate. Then, when the imaging plate is removed from the X-ray diffractometer and mounted on the reading device, the image information of the diffraction ring is read from the imaging plate, and the evaluation device analyzes this image information of the diffraction ring to evaluate the residual stress of the rail 1 and the like. And in Patent Document 2, the case of measuring the stress of the railway rail by the cosα method is taken as an example for explanation.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, in the diffraction ring forming device of Patent Document 1 and the X-ray diffractometer of Patent Document 2, including devising cases and the like, the emission angle of the X-ray is strictly adjusted and managed inside the device in advance. Therefore, there is no uncertainty in the emission angle of the X-ray, and no error occurs in the residual stress or the like. However, when the X-ray emitter is detachable, it is difficult to strictly adjust and manage the emission angle of the X-ray, and an error may occur in the residual stress or the like due to the uncertainty of the emission angle of the X-ray.

[0008] The present invention has been made in view of such circumstances, and an object thereof is to provide an X-ray diffraction measurement device capable of correctly calculating the residual stress of a measurement object OB even when the imaging surface and the X-ray are not orthogonal, and a method for calculating the residual stress by the X-ray diffraction measurement device.

Means for Solving the Problem

[0009] The X-ray diffraction measurement apparatus according to claim 1 includes correction calculation means for calculating information on the positional relationship between the optical axis of X-rays used by the residual stress calculation means and the imaging surface. The diffraction ring formation detection means detects the first diffraction ring of the first sample with a known diffraction angle in advance and also detects the second diffraction ring of the second sample with a known diffraction angle in advance and a diffraction angle different from that of the first sample. The correction calculation means includes sample diffraction ring centroid position coordinate calculation means for obtaining the centroid position coordinates of the first diffraction ring and the centroid position coordinates of the second diffraction ring, and X-ray optical axis inclination calculation means for obtaining the X-ray optical axis inclination, which is the inclination of the optical axis of X-rays with respect to the imaging surface, from the centroid position coordinates of the diffraction ring of the first sample and the centroid position coordinates of the diffraction ring of the second sample. The X-ray diffraction measurement apparatus also includes X-ray emission point coordinate calculation means for obtaining the X-ray emission point coordinates of the imaging surface when the distances from the imaging surface to the first sample and the second sample are zero. The residual stress calculation means corrects the centroid coordinates of the diffraction ring of the measurement object detected by the diffraction ring formation detection means based on the X-ray optical axis inclination and the X-ray emission point coordinates of the imaging surface calculated by the correction calculation means, and calculates the residual stress of the measurement object.

[0010] The X-ray diffraction measurement apparatus according to claim 2, in addition to the configuration of claim 1, the residual stress calculation means obtains the provisional centroid coordinates and the average radius of the diffraction ring of the measurement object detected by the diffraction ring formation detection means, obtains the centroid coordinate deviation when there is no X-ray optical axis inclination based on the provisional centroid coordinates and a known diffraction angle when there is no residual stress in the measurement object, adds the centroid coordinate deviation to the X-ray emission point coordinates to obtain the corrected centroid coordinates, re-aligns the corrected centroid coordinates as the origin to obtain the corrected diffraction angle for the entire circumference of the diffraction ring, and calculates the residual stress of the measurement object from the corrected diffraction angle.

[0011] The X-ray diffraction measurement apparatus according to claim 3, in addition to the configuration of claim 1 or claim 2, the residual stress calculation means calculates the residual stress using the cosα method.

[0012] The method for calculating residual stress of the X-ray diffraction measurement apparatus according to claim 4 includes detecting a first diffraction ring of a first sample with a known diffraction angle in advance, and detecting a second diffraction ring of a second sample with a known diffraction angle in advance and a diffraction angle different from that of the first sample. The centroid position coordinates of the first diffraction ring are obtained, and the centroid position coordinates of the second diffraction ring are obtained. From the centroid position coordinates of the diffraction ring of the first sample and the centroid position coordinates of the diffraction ring of the second sample, the X-ray optical axis tilt, which is the tilt of the X-ray optical axis with respect to the imaging plane, is obtained. The X-ray emission point coordinates of the imaging plane when the distances to the imaging plane, the first sample, and the second sample are zero are obtained. Based on the calculated X-ray optical axis tilt and the X-ray emission point coordinates of the imaging plane, the diffraction ring of the measurement object is detected, and the centroid coordinates of the detected diffraction ring of the measurement object are corrected to calculate the residual stress of the measurement object.

[0013] The method for calculating residual stress of the X-ray diffraction measurement apparatus according to claim 5, in addition to the configuration of claim 4, includes obtaining the provisional centroid coordinates and the average radius of the diffraction ring of the detected measurement object, and obtaining the centroid coordinate deviation when there is no X-ray optical axis tilt from the provisional centroid coordinates based on a known diffraction angle when there is no residual stress in the measurement object. The corrected centroid coordinates are obtained by adding the centroid coordinate deviation to the X-ray emission point coordinates. The corrected diffraction angle for the entire circumference of the diffraction ring is obtained by re-centering the corrected centroid coordinates at the origin, and the residual stress of the measurement object is calculated from the corrected diffraction angle.

[0014] The method for calculating residual stress of the X-ray diffraction measurement apparatus according to claim 6, in addition to the configuration of claim 4 or claim 5, is characterized by calculating the residual stress using the cosα method.

Advantages of the Invention

[0015] According to the invention of the present application, even when the imaging plane and the X-ray are not orthogonal, the residual stress of the measurement object OB can be correctly calculated.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Embodiments for Carrying Out the Invention

[0017] Hereinafter, the embodiments of the present invention will be specifically described with reference to the drawings. FIG. 1 is an explanatory diagram showing an example of an X-ray diffraction measurement apparatus according to the present invention. FIG. 2 is an explanatory diagram showing the configuration of the X-ray diffraction measurement unit of the X-ray diffraction measurement apparatus. FIG. 3 is an explanatory diagram showing the configuration of the X-ray diffraction measurement unit of the X-ray diffraction measurement apparatus. FIG. 4 is an explanatory diagram showing the positional relationship of the imaging plate (IP) of the X-ray diffraction measurement apparatus. FIG. 5 is an explanatory diagram showing the deviation of the center of gravity of the diffraction ring of the X-ray diffraction measurement apparatus. FIG. 6 is an explanatory diagram showing the state of correction of the X-ray diffraction measurement apparatus. FIGS. 7 and 8 are explanatory diagrams showing the details of the state of correction of the X-ray diffraction measurement apparatus.

[0018] The X-ray diffraction measurement apparatus 1 according to the present invention emits X-rays toward a measurement object OB to be measured, and calculates the residual stress of the measurement object OB. The X-ray diffraction measurement apparatus 1 includes an X-ray emitter 20 that emits X-rays toward the measurement object OB to be measured, irradiates the measurement object OB with X-rays from the X-ray emitter 20, and receives the diffracted light of the X-rays generated by the measurement object OB on an imaging plane that intersects the optical axis of the X-rays emitted from the X-ray emitter 20, forms a diffraction ring that is an image of the diffracted light of the X-rays on the imaging plane, and a diffraction ring formation detection means for detecting the diffraction ring, and a residual stress calculation means for calculating the residual stress of the measurement object OB from the data of the diffraction ring detected by the diffraction ring formation detection means.

[0019] The configuration of the X-ray diffraction measurement apparatus 1 including the diffraction ring forming apparatus 10 will be described with reference to FIGS. 1 to 3. This X-ray diffraction measurement apparatus 1 irradiates the measurement object OB with X-rays in order to measure the residual stress of the measurement object OB, and detects the shape of the diffraction ring formed by the diffracted X-rays emitted from the measurement object OB by the irradiation of the X-rays. In the present embodiment, the measurement object OB is a metal member. Also, the physical configuration of FIGS. 1 to 3 is an example.

[0020] The X-ray diffraction measurement apparatus 1 is composed of a diffraction ring forming apparatus 10 and others. The diffraction ring forming apparatus 10 includes, in a housing 12, an X-ray emitter 20 that emits X-rays, a table 52 for attaching an imaging plate 50 on which a diffraction ring is formed by diffracted X-rays, a table drive mechanism 30 that rotates and moves the table 52, a laser detection device 70 for measuring the shape of the diffraction ring formed on the imaging plate (IP) 50, and includes the X-ray emitter 20, the imaging plate 50, the table 52, the table drive mechanism 30, and the laser detection device 70. Further, the X-ray diffraction measurement apparatus 1 also includes a computer device 100 and a high voltage power supply 110.

[0021] In addition, inside the diffraction ring forming device 10, various circuits for operation control and input of detection signals by being connected to the X-ray emitter 20, the table 52, the table drive mechanism 30, and the laser detection device 70 are also built in. The various circuits shown outside the diffraction ring forming device 10 (housing 12) in FIG. 1 are housed within the two-dot chain line inside the diffraction ring forming device 10. In FIGS. 1 to 3, circuit boards, electric wires, fixtures, air-cooling fans, etc. are omitted.

[0022] As shown in FIG. 1, the housing 12 of the diffraction ring forming device 10 has a rectangular parallelepiped shape with a slope formed on the bottom surface to eliminate corners and a stepped structure on the bottom surface. Specifically, the housing 12 has a first bottom wall 12a, a second bottom wall 12c, a front wall 12b, a rear wall 12e, an upper wall 12f, side walls (not shown), a bottom inclined wall 12g connecting the first bottom wall 12a and the second bottom wall 12c, and a connecting wall 12d provided to eliminate the corner where the second bottom wall 12c and the front wall 12b intersect. And, in the second bottom wall 12c, there is a circular hole 12c1 through which the X-ray emitted from the X-ray emitter 20 and the diffracted X-ray generated by the measurement object OB pass.

[0023] As shown in FIG. 1, the X-ray emitter 20 is formed in a long shape, extends in the horizontal direction (left - right direction in the figure) at the upper part inside the housing 12, and is fixed to the housing 12. It receives a high voltage supply from the high voltage power supply 110 and is controlled by the X-ray control circuit 200 to emit X-rays downward (in the lower left direction in the figure) from the emission port 22. The direction of the emission port 22 is such that the optical axis of the emitted X-ray is in a direction substantially orthogonal to the second bottom wall 12c. And when the surface of the measurement object OB is parallel to the connecting wall 12d, the incident angle of the X-ray with respect to the surface of the measurement object OB is approximately 45 degrees.

[0024] The X-ray control circuit 200 is controlled by the controller 102 that constitutes the computer device 100 described later, and controls the drive current and drive voltage supplied from the high-voltage power supply 110 to the X-ray emitter 20 so that X-rays of a certain intensity are emitted from the X-ray emitter 20. Further, the X-ray emitter 20 is provided with a cooling device (not shown), and the X-ray control circuit 200 also controls the drive signal supplied to this cooling device. Thereby, the temperature of the X-ray emitter 20 is kept constant.

[0025] As shown in FIGS. 1 to 3, the table drive mechanism 30 includes a moving stage 32 below the X-ray emitter 20. The moving stage 32 can move in a direction perpendicular to the optical axis of the X-rays emitted from the X-ray emitter 20 within the plane formed by the optical axis of the X-rays and the normal line of the measurement object OB by the feed motor 34 and the screw rod 36. The feed motor 34 is fixed within the table drive mechanism 30 and is immovable with respect to the housing 12. The screw rod 36 extends in a direction perpendicular to the optical axis of the X-rays emitted from the X-ray emitter 20, and one end thereof is connected to the output shaft of the feed motor 34. The other end of the screw rod 36 is rotatably supported by a bearing portion 38 provided within the table drive mechanism 30.

[0026] Further, the moving stage 32 is sandwiched by a pair of opposing plate-like guides 40, 40 fixed within the table drive mechanism 30, respectively, and can move along the axial direction of the screw rod 36. That is, when the feed motor 34 is driven forward or backward, the rotational motion of the feed motor 34 is converted into the linear motion of the moving stage 32. An encoder 34a is incorporated in the feed motor 34. Each time the feed motor 34 rotates by a predetermined minute rotation angle, the encoder 34a outputs a pulse train signal that alternates between a high level and a low level to the position detection circuit 202 and the feed motor control circuit 204.

[0027] The position detection circuit 202 and the feed motor control circuit 204 are activated according to commands from the controller 102. Immediately after the measurement starts, the feed motor control circuit 204 drives the feed motor 34 to move the moving stage 32 toward the feed motor 34 side. When the pulse train signal output from the encoder 34a stops being input to the position detection circuit 202, the position detection circuit 202 outputs a signal indicating that the moving stage 32 has reached the movement limit position to the feed motor control circuit 204 and sets the count value to "0". When the feed motor control circuit 204 receives a signal from the position detection circuit 202 indicating that the movement limit position has been reached, the feed motor control circuit 204 stops outputting the drive signal to the feed motor 34. The above movement limit position is set as the origin position of the moving stage 32. Therefore, when the moving stage 32 moves in the upper left direction in FIG. 1 and reaches the movement limit position, the position detection circuit 202 outputs a position signal representing "0". When the moving stage 32 moves from the movement limit position in the lower right direction, the position detection circuit 202 counts the pulse train signal from the encoder 34a and outputs a signal representing the movement distance x from the movement limit position as the position signal.

[0028] When the feed motor control circuit 204 receives a set value representing the destination position of the moving stage 32 from the controller 102, the feed motor control circuit 204 drives the feed motor 34 to rotate forward or backward according to the set value. The position detection circuit 202 counts the number of pulses of the pulse signal output by the encoder 34a. Then, the position detection circuit 202 calculates the current position of the moving stage 32 (the movement distance x from the movement limit position) using the counted number of pulses and outputs it to the controller 102 and the feed motor control circuit 204. The feed motor control circuit 204 drives the feed motor 34 until the current position of the moving stage 32 input from the position detection circuit 202 matches the destination position input from the controller 102.

[0029] In addition, the feed motor control circuit 204 inputs a set value representing the moving speed of the moving stage 32 from the controller 102. Then, using the number of pulses per unit time of the pulse signal input from the encoder 34a, it calculates the moving speed of the moving stage 32, and drives the feed motor 34 so that the calculated moving speed of the moving stage 32 becomes the moving speed input from the controller 102.

[0030] The upper ends of the pair of guides 40, 40 are connected by a plate-shaped upper wall 42. As shown in FIG. 3, the upper wall 42 is provided with a through hole 42a, and the center position of the through hole 42a faces the center position of the emission port 22 of the X-ray emitter 20. The X-ray emitted from the X-ray emitter 20 enters the table drive mechanism 30 through the emission port 22 and the through hole 42a.

[0031] In a state where the imaging plate 50 to be described later is at the diffraction ring imaging position (the state shown in FIGS. 1 to 3), a through hole 32a is formed at a position facing the through hole 42a of the moving stage 32. A spindle motor 44 having an output shaft 44a with the center axis position of the emission port 22 and the through holes 42a and 32a as the rotation center is assembled to the moving stage 32. The output shaft 44a is formed in a cylindrical shape and has a through hole 44a1 with a circular cross-section centered on the rotation center. On the side opposite to the output shaft 44a of the spindle motor 44, a through hole 44b centered on the center position of the through hole 44a1 is provided. A cylindrical passage member 46 for reducing a part of the inner diameter of the through hole 44b is fixed on the inner peripheral surface of the through hole 44b.

[0032] Also, an encoder 44c similar to the encoder 34a is incorporated in the spindle motor 44. Each time the spindle motor 44 rotates by a predetermined minute rotation angle, the encoder 44c outputs a pulse train signal that alternates between a high level and a low level to the spindle motor control circuit 206 and the rotation angle detection circuit 208. Further, each time the spindle motor 44 makes one rotation, the encoder 44c outputs an index signal that switches from a low level to a high level for a predetermined short period to the controller 102 and the rotation angle detection circuit 208.

[0033] The spindle motor control circuit 206 and the rotation angle detection circuit 208 are activated by a command from the controller 102. The spindle motor control circuit 206 receives a set value representing the rotation speed of the spindle motor 44 from the controller 102. Then, it calculates the rotation speed of the spindle motor 44 using the number of pulses per unit time of the pulse signal input from the encoder 44c, and supplies a drive signal to the spindle motor 44 so that the calculated rotation speed becomes the rotation speed (set value) input from the controller 102. The rotation angle detection circuit 208 counts the number of pulses of the pulse train signal output from the encoder 44c, calculates the rotation angle of the spindle motor 44, that is, the rotation angle θp of the imaging plate 50, using the count value, and outputs it to the controller 102. When the rotation angle detection circuit 208 receives the index signal output from the encoder 44c, it sets the count value to "0". That is, the position where the index signal is input is the reference position of the rotation angle of 0 degrees.

[0034] The table 52 is formed in a circular shape and is fixed to the tip of the output shaft 44a of the spindle motor 44. The central axis of the table 52 coincides with the central axis of the output shaft 44a of the spindle motor 44. The table 52 is integrally provided with a protruding portion 54 that protrudes downward from the center of the lower surface, and a screw thread is formed on the outer peripheral surface of the protruding portion 54. The central axis of the protruding portion 54 coincides with the central axis of the output shaft 44a of the spindle motor 44. The imaging plate 50 is attached to the lower surface of the table 52.

[0035] The imaging plate 50 is a circular plastic film with a phosphor applied to its surface. The lower surface of the imaging plate 50 (the surface on the side of the object to be measured OB) serves as the imaging surface for forming diffraction rings. A through-hole 50a is provided at the center of the imaging plate 50. By passing the protruding portion 54 through this through-hole 50a and screwing a nut-shaped fixture 56 onto the outer peripheral surface of the protruding portion 54, the imaging plate 50 is sandwiched and fixed between the fixture 56 and the table 52. The fixture 56 is a cylindrical member, and a thread corresponding to the thread of the protruding portion 54 is formed on its inner peripheral surface.

[0036] Through-holes 52a, 54a, and 56a are also provided in the table 52, the protruding portion 54, and the fixture 56, respectively. The central axes of the through-holes 52a, 54a, and 56a are the same as the central axis of the table 52. The inner diameter of the through-hole 56a is smaller than those of the through-holes 52a and 54a and is the same as the inner diameter of the aforementioned passage member 46. Therefore, the X-rays emitted from the output shaft 44a of the spindle motor 44 are emitted toward the object to be measured OB located externally below through the through-holes 52a, 54a, and 56a and through the circular hole 12c1 provided in the second bottom wall 12c. In this case, since the inner diameter of the passage member 46 and the inner diameter of the through-hole 56a are small, the X-rays incident into the through-holes 44b, 44a1, 52a, and 54a through the passage member 46 are slightly diffused, but the X-rays emitted from the through-hole 56a become parallel light parallel to the axis of the through-hole 44a1 and are emitted from the circular hole 12c1.

[0037] The imaging plate 50 is driven by the feed motor 34 and moves together with the moving stage 32, the spindle motor 44, and the table 52 from the origin position to the diffraction ring imaging position for imaging the diffraction ring. As described above, at this diffraction ring imaging position, the X-rays emitted from the X-ray emitter 20 are irradiated onto the measurement object OB on the table TB. Further, the imaging plate 50 is driven by the spindle motor 44 to rotate, and is driven by the feed motor 34 to move within the diffraction ring reading area for reading the imaged diffraction ring and within the diffraction ring erasing area for erasing the diffraction ring, together with the moving stage 32, the spindle motor 44, and the table 52. In the movement of the imaging plate 50 in this case, the central axis of the imaging plate 50 is maintained within the plane formed by the optical axis of the X-rays emitted from the X-ray emitter 20 and the normal line of the measurement object OB, and moves in a direction perpendicular to the optical axis of the X-rays.

[0038] The laser detection device 70 irradiates the imaging plate 50 that has imaged the diffraction ring with laser light and detects the intensity of the light incident from the imaging plate 50. The laser detection device 70 is sufficiently separated from the measurement object OB and the imaging plate 50 at the diffraction ring imaging position toward the feed motor 34 side. That is, when the imaging plate 50 is at the diffraction ring imaging position, the X-rays diffracted by the measurement object OB are not blocked by the laser detection device 70. The laser detection device 70 includes a laser light source 72, a collimating lens 74, a reflecting mirror 76, a polarization beam splitter 78, a quarter-wave plate 80, and an objective lens 82.

[0039] The laser light source 72 is controlled by the laser drive circuit 210 to emit laser light for irradiating the imaging plate 50. The laser drive circuit 210 is controlled by the controller 102 and controls and supplies a drive signal so that laser light of a predetermined intensity is emitted from the laser light source 72. The laser drive circuit 210 inputs the light reception signal output from the photodetector 94 described later and controls the drive signal output to the laser light source 72 so that the intensity of the light reception signal becomes a predetermined intensity. Thereby, the intensity of the laser light irradiated on the imaging plate 50 is maintained constant.

[0040] The collimating lens 74 converts the laser light emitted from the laser light source 72 into parallel light. The reflecting mirror 76 reflects the laser light converted into parallel light by the collimating lens 74 toward the polarization beam splitter 78. The polarization beam splitter 78 transmits most (for example, 95%) of the laser light incident from the reflecting mirror 76 as it is. The quarter-wave plate 80 converts the laser light incident from the polarization beam splitter 78 from linearly polarized light to circularly polarized light. The objective lens 82 condenses the laser light incident from the quarter-wave plate 80 on the surface of the imaging plate 50. The optical axis of the laser light emitted from the objective lens 82 is within the plane formed by the optical axis of the X-ray emitted from the X-ray emitter 20 and the normal line of the measurement object OB, and is in a direction parallel to the optical axis of the X-ray, that is, a direction perpendicular to the moving direction of the moving stage 32.

[0041] A focus actuator 84 is assembled to the objective lens 82. The focus actuator 84 is an actuator that moves the objective lens 82 in the optical axis direction of the laser light. Incidentally, the objective lens 82 is located at the center of its movable range when the focus actuator 84 is not energized.

[0042] When the laser light condensed by the objective lens 82 is irradiated onto the surface of the imaging plate 50 at the portion where the diffraction ring is imaged, a photo-stimulated luminescence phenomenon occurs. That is, after imaging the diffraction ring, when the imaging plate 50 is irradiated with laser light, the phosphor of the imaging plate 50 emits light that is light corresponding to the intensity of the diffracted X-rays and has a wavelength shorter than the wavelength of the laser light. The reflected light of the laser light irradiated onto and reflected from the imaging plate 50 and the light emitted from the phosphor pass through the objective lens 82 and the quarter-wave plate 80 and are reflected by the polarization beam splitter 78.

[0043] In the reflection direction of the polarization beam splitter 78, a condenser lens 86, a cylindrical lens 88, and a photodetector 90 are provided. The condenser lens 86 condenses the light incident from the polarization beam splitter 78 onto the cylindrical lens 88. The cylindrical lens 88 causes astigmatism in the transmitted light. The photodetector 90 is composed of a four-segment light-receiving element consisting of four identical square light-receiving elements separated by dividing lines, and outputs detection signals having magnitudes proportional to the intensities of the light incident on the four light-receiving regions arranged clockwise as four light-receiving signals to the amplifier circuit 212.

[0044] The amplifier circuit 212 amplifies each of the four light-receiving signals output from the photodetector 90 with the same amplification factor to generate four light-receiving signals, and outputs them to the focus error signal generation circuit 214 and the SUM signal generation circuit 216. In this embodiment, focus servo control by the astigmatism method is used. The focus error signal generation circuit 214 generates a focus error signal by calculation using the four amplified light-receiving signals. That is, the focus error signal generation circuit 214 performs a predetermined calculation and outputs the calculation result as a focus error signal to the focus servo circuit 218. The focus error signal represents the amount of deviation of the focal position of the laser light from the surface of the imaging plate 50.

[0045] The focus servo circuit 218 is controlled by the controller 102, and generates a focus servo signal based on the focus error signal and outputs it to the drive circuit 220. The drive circuit 220 drives the focus actuator 84 according to this focus servo signal, and displaces the objective lens 82 in the optical axis direction of the laser light. In this case, by generating the focus servo signal so that the value of the focus error signal always becomes a constant value (for example, zero), the laser light can be continuously focused on the surface of the imaging plate 50.

[0046] The SUM signal generation circuit 216 adds up the amplified four light reception signals to generate a SUM signal and outputs it to the A / D conversion circuit 222. The intensity of the SUM signal corresponds to the combined intensity of the laser light reflected by the imaging plate 50 and the light generated by the cathodoluminescence. However, since the intensity of the laser light reflected by the imaging plate 50 is almost constant, the intensity of the SUM signal corresponds to the intensity of the light generated by the cathodoluminescence. That is, the intensity of the SUM signal corresponds to the intensity of the diffracted X-rays incident on the imaging plate 50. The A / D conversion circuit 222 is controlled by the controller 102, inputs the SUM signal from the SUM signal generation circuit 216, converts the instantaneous value of the input SUM signal into digital data, and outputs it to the controller 102.

[0047] Also, the laser detection device 70 includes a condenser lens 92 and a photodetector 94. The condenser lens 92 condenses, on the light receiving surface of the photodetector 94, a part of the laser light emitted from the laser light source 72, which is the laser light reflected without passing through the polarization beam splitter 78. The photodetector 94 is a light receiving element that outputs a light reception signal corresponding to the intensity of the light condensed on the light receiving surface. Therefore, the photodetector 94 outputs a light reception signal corresponding to the intensity of the laser light emitted from the laser light source 72 to the laser drive circuit 210.

[0048] Also, an LED light source 96 is provided adjacent to the objective lens 82. The LED light source 96 is controlled by an LED drive circuit 224 to emit visible light to erase the diffraction rings imaged on the imaging plate 50. The LED drive circuit 224 is controlled by the controller 102 and supplies a drive signal for causing the LED light source 96 to emit visible light of a predetermined intensity.

[0049] Also, as shown in FIGS. 2 and 3, the diffraction ring forming device 10 has an LED light source 60. The LED light source 60 is fixed to the lower surface of one end of a plate 62 disposed between the X-ray emitter 20 and the upper wall 42 of the table drive mechanism 30. The plate 62 is fixed to the output shaft 64a of a motor 64 fixed within the housing 12 at the upper surface of the other end thereof, and rotates in a plane parallel to the upper wall 42 of the table drive mechanism 30 by the rotation of the motor 64. Stopper members 68a and 68b are provided on the upper wall 42 of the table drive mechanism 30. When the plate 62 is rotated, the stopper member 68a restricts the rotation of the plate 62 so that the LED light source 60 stops at a position (P position) facing the emission port 22 of the X-ray emitter 20 and the through hole 42a of the upper wall 42 of the table drive mechanism 30.

[0050] On the other hand, when the plate 62 is rotated, the stopper member 68b restricts the rotation of the plate 62 so that the plate 62 stops at a position (S position) where it does not block the space between the emission port 22 of the X-ray emitter 20 and the through hole 42a of the upper wall 42 of the table drive mechanism 30. In other words, the P position is the position where the plate 62 is in the state shown in FIGS. 1 to 3, and is the position where the LED light emitted from the LED light source 60 enters the passage of the passage member 46 provided in the through hole 44a1 of the spindle motor 44. The S position is the position where the X-ray emitted from the X-ray emitter 20 is not blocked by the plate 62.

[0051] The LED light source 60 emits LED light by a drive signal from an LED drive circuit 226 that is operationally controlled by a controller 102. The LED light is diffused visible light, and when the plate 62 is in the P position, a part of it enters through the through holes 42a, 32a, the passage of the passage member 46, and the through hole 44b, and enters the through hole 44a1 of the output shaft 44a of the spindle motor 44, and is emitted from the through holes 52a, 54a, 56a and the circular hole 12c1 of the second bottom wall 12c. Also in the case of this LED light, since the inner diameter of the passage member 46 and the inner diameter of the through hole 56a are small, the X-rays that enter the through holes 44b, 44a1, 52a, 54a through the passage member 46 are slightly diffused, but the LED light emitted from the through hole 56a becomes parallel light parallel to the axis of the through hole 44a1 and is emitted from the circular hole 12c1. Therefore, the LED light source 60, the passage member 46, the through hole 56a, etc. constitute the visible light emitter of the present invention that emits parallel light that is visible light to the measurement object OB.

[0052] The motor 64 is provided with an encoder 64b similar to the encoders 34a, 44c, and the encoder 64b outputs a pulse train signal that alternates between a high level and a low level to the rotation control circuit 228 each time the motor 64 rotates by a predetermined minute rotation angle. When an instruction of the rotation direction and the start of rotation is input from the controller 102 to the rotation control circuit 228, the rotation control circuit 228 outputs a drive signal to the motor 64 to rotate the motor 64 in the instructed direction. Then, when the input of the pulse train signal from the encoder 64b stops, the output of the drive signal stops. Thereby, the plate 62 can be rotated to the above-described P position and S position, respectively.

[0053] An imaging lens 24 is provided on the bottom inclined wall 12g of the housing 12, and an imager 26 is provided inside the housing 12. The imager 26 is composed of a CCD light receiver or a CMOS light receiver in which a large number of imaging elements are arranged in a matrix, and outputs a light reception signal (imaging signal) of a magnitude corresponding to the intensity of light received by each imaging element to a sensor signal extraction circuit 230 for each imaging element. These imaging lens 24 and imager 26 image an image of a region centered on the emission point of the LED light on the measurement object OB at a position set with respect to the imaging plate 50.

[0054] That is, the imaging lens 24 and the imager 26 function as a digital camera that images the measurement object OB. The position set with respect to this imaging plate 50 is a position where the vertical distance L from the emission point (irradiation point) of the X-ray and the LED light on the measurement object OB to the imaging plate 50 is a predetermined distance Lo. In addition, the depth of field of the imaging lens 24 and the imager 26 in this case is set in the front and rear ranges centered on the emission point. The sensor signal extraction circuit 230 outputs the light reception signal (imaging signal) from each imaging element of the imager 26 to the controller 102 together with data indicating the position of each imaging element (that is, the pixel position). Therefore, image data representing an image in the vicinity of the irradiation point including the irradiation point of the LED light on the measurement object OB is output to the controller 102.

[0055] The computer device 100 consists of a controller 102, an input device 104, and a display device 106. The controller 102 is an electronic control device mainly composed of a microcomputer equipped with a CPU, ROM, RAM, a mass storage device, etc., and executes various programs stored in the mass storage device to control the operation of the X-ray diffraction measurement device 1. Further, the diffraction ring formation detection means, residual stress calculation means, correction calculation means, sample diffraction ring centroid position coordinate calculation means, X-ray optical axis inclination calculation means, and X-ray emission point coordinate calculation means, which will be described later, are realized by the controller 102. The input device 104 is connected to the controller 102 and is used by an operator for inputting various parameters, operation instructions, etc. The display device 106 displays, in addition to the image including the irradiation point imaged by the imager 26 on the display screen, marks for appropriately setting the position and orientation of the measurement object OB of the housing 12. Further, the display device 106 also visually informs the operator of various setting statuses, operation statuses, measurement results, etc. The high-voltage power supply 110 supplies a high voltage and current for X-ray emission to the X-ray emitter 20.

[0056] In the X-ray diffraction measurement device 1 configured as described above, when calculating the residual stress of the measurement object OB, the value is greatly affected by the positional relationship between the imaging plate (IP) 50 constituting the imaging surface and the X-ray. Particularly when using the socα method, the positional relationship between the imaging plate (IP) 50 and the X-ray becomes extremely important. The X-ray hitting the measurement object OB causes diffraction and reflects in a conical shape centered on the axis of the apparent X-ray (see Fig. 4). Here, when there is stress in the sample in the measurement object OB, the reflected cone appears to shift, so the positional relationship between the imaging plate (IP) 50 and the X-ray becomes a problem. In conventional X-ray diffraction measurement devices, at the manufacturing, assembly, and initial adjustment stages of the X-ray diffraction measurement device, the positional relationship between the imaging plate and the X-ray is established as the positional relationship most suitable for calculating the residual stress, and strict fixation of the positional relationship is performed so that no error occurs in subsequent measurements.

[0057] Specifically, if the distance between the object to be measured OB and the imaging plate (IP) 50 (hereinafter referred to as the sample distance) is fixed, the imaging plate (IP) 50 as the imaging surface and the X-ray do not necessarily have to be orthogonal. However, when they are not orthogonal, the positional relationship between the imaging plate (IP) 50 and the X-ray irradiation point changes, and the centroid of the diffraction ring changes. As shown in FIGS. 4 and 5, in the case of sample A which is the first sample and sample B which is the second sample, which are two samples with different diffraction angles of the diffraction ring, compared with the centroid (X0, Y0) of the diffraction ring in the case of the ideal position of the imaging plate (IP) 50 (orthogonal to the X-ray), the positions of the centroid (XDA0, YDA0) of the diffraction ring A (RDA) of sample A and the centroid (XDB0, YDB0) of the diffraction ring B (RDB) of sample B are at different positions respectively. In order to prevent such a shift in the centroid of each diffraction ring, in a conventional X-ray diffraction measurement apparatus, the imaging plate (IP) 50 and the X-ray are adjusted to be orthogonal. As shown below, the present invention is for correctly calculating the residual stress of the object to be measured OB even when the imaging plate (IP) 50 and the X-ray are not orthogonal (the imaging surface is substantially perpendicular to the optical axis of the X-ray (although it is almost perpendicular, it is not perpendicular enough to accurately calculate the residual stress in the calculation of the residual stress)).

[0058] Hereinafter, a specific description of the present invention will be given. First, as a conventional basic means of the X-ray diffraction measurement apparatus 1, a specific method for obtaining the residual stress of the object to be measured OB by forming a diffraction ring and detecting its shape will be described. In this measurement of the residual stress, the X-ray diffraction measurement apparatus 1 is configured as shown in FIGS. 1 to 3, and the operation of the X-ray diffraction measurement apparatus 1 is started by turning on the power supply. Then, the object to be measured OB is placed on the table TB, and the diffraction ring formation detection means and the residual stress calculation means are made to function.

[0059] The diffraction ring formation detection means operates the X-ray emitter 20 to irradiate the object to be measured OB with X-rays, records the diffraction ring on the imaging plate 50, and operates the laser detection device 70 to read the diffraction ring recorded on the imaging plate 50. Here, although the object to be measured OB is described, the same applies to the case of the sample A and the sample B. Then, the LED light source 96 is operated to erase the diffraction ring recorded on the imaging plate 50, and the residual stress of the object to be measured OB is calculated using the data representing the diffraction ring read by the residual stress calculation means. In addition, in the residual stress calculation means of the present application, the cosα method is used as a method for calculating the residual stress, but it is not limited to the cosα method.

[0060] Hereinafter, even when the imaging plate (IP) 50 and the X-rays of the present invention are not orthogonal, the correction for correctly calculating the residual stress of the object to be measured OB will be described (for the following description and the symbols in the calculation formulas, refer to FIGS. 4 to 8. Also, for each symbol, the symbols of X, Y, x, and y indicate the respective dimensions of the X-axis and the Y-axis). The X-ray diffraction measurement apparatus 1 of the present application has a diffraction ring formation detection means and a residual stress calculation means having functions to be described later in addition to the conventional functions, and also includes a correction calculation means for calculating information on the positional relationship between the optical axis of the X-rays used by the residual stress calculation means and the imaging surface (IP).

[0061] As for the functional configuration, the diffraction ring formation detection means detects the diffraction ring A (RDA) (the first diffraction ring) of sample A, which is the first sample with a known diffraction angle in advance, and detects the diffraction ring B (RDB) (the second diffraction ring) of sample B, which is the second sample with a known diffraction angle in advance and a diffraction angle different from that of the first sample. (Note that RD represents the average radius of each diffraction ring.) Further, the correction calculation means includes a sample diffraction ring centroid position coordinate calculation means for obtaining the centroid position coordinates (XDA0, YDA0) of the diffraction ring A and the centroid position coordinates (XDB0, YDB0) of the diffraction ring B, and an X-ray optical axis inclination calculation means for obtaining the inclination of the X-ray optical axis (ρx, ρy) with respect to the imaging plane from the centroid position coordinates (XDA0, YDA0) of the diffraction ring A and the centroid position coordinates (XDB0, YDB0) of the diffraction ring B, and an X-ray emission point coordinate calculation means for obtaining the X-ray emission point coordinates (X0, Y0) of the imaging plane when the distances from the imaging plane (IP) to sample A and sample B are zero.

[0062] Then, the residual stress calculation means corrects the centroid coordinates of the diffraction ring of the measurement object OB detected by the diffraction ring formation detection means based on the X-ray optical axis inclination (ρx, ρy) calculated by the correction calculation means and the X-ray emission point coordinates (X0, Y0) on the imaging plane (IP), and calculates the residual stress of the measurement object OB. Specifically, the residual stress calculation means obtains the provisional centroid coordinates and the average radius RD of the diffraction ring of the measurement object OB detected by the diffraction ring formation detection means, obtains the centroid coordinate deviation when there is no X-ray optical axis inclination based on the known diffraction angle when there is no residual stress in the measurement object OB, adds the centroid coordinate deviation to the X-ray emission point coordinates (X0, Y0) to obtain the corrected centroid coordinates (XD0, YD0), re-aligns with the corrected centroid coordinates (XD0, YD0) as the origin to obtain the corrected diffraction angle for the entire circumference of the diffraction ring, and calculates the residual stress of the measurement object OB from the corrected diffraction angle.

[0063] As for the operation flow, first, the diffraction ring A (RDA) of sample A is detected, and at the same time, the second diffraction ring of sample B (RDB) is detected. Then, the centroid position coordinates (XDA0, YDA0) of diffraction ring A are obtained, and the centroid position coordinates (XDB0, YDB0) of diffraction ring B are obtained. Next, from the centroid position coordinates (XDA0, YDA0) of diffraction ring A and the centroid position coordinates (XDB0, YDB0) of diffraction ring B of sample B, the X-ray optical axis inclination (ρx, ρy) with respect to the imaging plane (IP) is obtained. Next, the X-ray emission point coordinates (X0, Y0) on the imaging plane (IP) when the distances to sample A and sample B are set to zero are obtained. Then, based on the calculated X-ray optical axis inclination (ρx, ρy) and the X-ray emission point coordinates (X0, Y0) of the imaging plane, the diffraction ring of the measurement object OB is detected, and the centroid coordinates of the detected diffraction ring of the measurement object OB are corrected to calculate the residual stress of the measurement object OB.

[0064] The specific process of correcting the centroid coordinates of the detected diffraction ring of the measurement object OB to calculate the residual stress of the measurement object OB is as follows: First, the provisional centroid coordinates and the average radius RD of the detected diffraction ring of the measurement object OB are obtained. Then, based on the known diffraction angle when there is no residual stress in the measurement object OB, the centroid coordinate deviation when there is no provisional centroid coordinate and X-ray optical axis inclination is obtained, and the centroid coordinate deviation is added to the X-ray emission point coordinates (X0, Y0) to obtain the corrected centroid coordinates (XD0, YD0). Then, the corrected diffraction angle of the entire circumference of the diffraction ring is obtained with the corrected centroid coordinates (XD0, YD0) as the origin, and the residual stress of the measurement object OB is calculated from the corrected diffraction angle.

[0065] Next, the flow of operations will be described based on mathematical formulas. First, when considering the X-axis direction (similarly for the Y-axis direction), assume that the actual imaging plane (IP) is inclined by ρx in the X-axis direction with respect to the ideal plane (a plane with no inclination, that is, the imaging plane when the imaging plane and the X-ray are orthogonal) (see Fig. 6). Let the centroids of diffraction rings A and B when converted to the ideal plane be XA0 and XB0, and let the coordinates of the X-ray emission point be X0. Then, as a coordinate transformation formula, it can be shown as in Figs. 7 and 8 and the following mathematical formulas. Here, when considering the conversion of the coordinate system to the ideal plane, the following formulas of Equation 1 and Equation 2 and Equation 3 for the X coordinate of the center on the ideal plane can be established (note that P and M respectively represent plus and minus, and plus indicates the right side in Fig. 6).

[0066]

Equation

[0067]

Equation

[0068]

Equation

[0069] Here, when considering the X coordinate, when the deviation of the center of diffraction ring A on the ideal plane when the imaging plane (IP) is inclined is XA, and the deviation of the center of diffraction ring B on the ideal plane when the imaging plane (IP) is inclined is XB, the measured XA0 and XB0 are the X-ray emission point + the inclination deviation amount, so they become the following Equation 4 and Equation 5, and Equation 6 is derived.

[0070]

Equation

[0071]

Equation

[0072]

Number

[0073] XA0 can be set as Equation 7, Equation 8, and Equation 9 by substituting RP = RAP and RM = RAM from the measured value and the conversion formula to the ideal surface. Since the diffraction ring B is the same as the diffraction ring A, Equation 10 is derived.

[0074]

Number

[0075]

Number

[0076]

Number

[0077]

Number

[0078] Substituting Equation 9 and Equation 10 into Equation 6 gives Equation 11, and Equation 12 is obtained.

[0079]

Number

[0080]

Number

[0081] Equation 14 can be derived from Equation 13 obtained by substituting Equation 9 into Equation 4.

[0082]

Number

[0083]

Math

[0084] Even if the number 10 is substituted into the number 5, the resulting number is still 15.

[0085]

Math

[0086] From these series of mathematical formulas, the emission point coordinates (X0, Y0) of the X-ray and the X-ray optical axis inclination (ρx, ρy) can be obtained.

[0087] The complementary angle 2η of the diffraction angle of the object to be measured OB is known from its material, and the average radius RD of the diffraction ring of the object to be measured OB obtained by the diffraction ring formation detection means is determined. Incidentally, the calculation of the average radius RD of each diffraction ring may use any of the known methods and is not particularly limited. Then, from the X-ray emission point coordinates (X0, Y0), the X-ray optical axis inclination (ρx, ρy), and the number 13, it becomes the numbers 16 to 17, and similarly for each mathematical formula of the number 18, the corrected centroid coordinates (XD0, YD0) of the object to be measured OB can be obtained.

[0088]

Math

[0089]

Math

[0090]

Math

[0091] Then, by the residual stress calculation means, the corrected diffraction angle of the entire circumference of the diffraction ring is obtained by re-setting the corrected centroid coordinates (XD0, YD0) as the origin, and the residual stress of the measurement object OB is calculated from the corrected diffraction angle.

[0092] According to the X-ray diffraction measurement apparatus 1 operating with such a configuration, even when the imaging plate (IP) 50 which is the imaging surface and the X-ray are not orthogonal, the residual stress of the measurement object OB can be correctly calculated.

[0093] The present invention can be implemented in various embodiments and modifications without departing from the broad spirit and scope of the present invention. Further, the above-described embodiments are for explaining the present invention and do not limit the scope of the present invention. That is, the scope of the present invention is indicated by the claims rather than the embodiments. And various modifications made within the scope of the claims and within the scope of the meaning of the invention equivalent thereto are regarded as being within the scope of this invention.

Industrial Applicability

[0094] As described above, according to the present invention, it is possible to provide an X-ray diffraction measurement apparatus capable of correctly calculating the residual stress of the measurement object OB even when the imaging surface and the X-ray are not orthogonal, and a method for calculating the residual stress by the X-ray diffraction measurement apparatus.

Explanation of Reference Numerals

[0095] 1 ······ X-ray diffraction measurement apparatus 10 ······ Diffraction ring forming apparatus 12 ······ Housing 12a ······ First bottom wall 12b ······ Front wall 12c ······ Second bottom wall 12c1 ····· Circular hole 12d ······ Connecting wall 12e ······ Rear wall 12f ······ Top wall 12g ······ Bottom inclined wall 20 ······ X-ray emitter 22 ······ Exit port 24 ······ Imaging lens 26 ······ Image sensor 30 ······ Table drive mechanism 32 ······ Moving stage 32a ······ Through hole 34 ······ Feed motor 34a ······ Encoder 36 ······ Screw rod 38 ······ Bearing part 40 ······ Guide 42 ······ Upper wall 42a ······ Through hole 44 ······ Spindle motor 44a ······ Output shaft 44b ······ Through hole 44c ······ Encoder 44a1 ······ Through hole 46 ······ Passage member 50 ······ Imaging plate 50a ······ Through hole 52 ······ Table 52a ······ Through hole 54 ······ Protrusion 54a ······ Through hole 56 ······ Fixture 56a ······ Through hole 60 ······ LED light source 62 ······ Plate 64 ······ Motor 64a ······ Output shaft 64b ······ Encoder 68a ······ Stopper member 68b ······ Stopper member 70 ······ Laser detection device 72 ······ Laser light source 74 ······ Collimating lens 76 ······ Reflecting mirror 78 ······ Polarizing beam splitter 80 ······ Quarter-wave plate 82 ······ Objective lens 84 ····· Focus actuator 86 ····· Condensing lens 88 ····· Cylindrical lens 90 ····· Photodetector 92 ····· Condensing lens 94 ····· Photodetector 96 ····· LED light source 100 ····· Computer device 102 ····· Controller 104 ····· Input device 106 ····· Display device 110 ····· High-voltage power supply 200 ····· X-ray control circuit 202 ····· Position detection circuit 204 ····· Feed motor control circuit 206 ····· Spindle motor control circuit 208 ····· Rotation angle detection circuit 210 ····· Laser drive circuit 212 ····· Amplification circuit 214 ····· Focus error signal generation circuit 216 ····· SUM signal generation circuit 218 ····· Focus servo circuit 220 ····· Drive circuit 222 ····· A / D conversion circuit 224 ····· LED drive circuit 226 ····· LED drive circuit 228 ····· Rotation control circuit 230 ····· Sensor signal extraction circuit

Claims

1. An X-ray diffractometer comprising: an X-ray emitter that emits X-rays toward a measurement object to be measured; an X-ray diffractometer that irradiates the measurement object with the X-rays from the X-ray emitter and receives diffracted light of the X-rays generated by the measurement object on an imaging surface that intersects substantially perpendicularly to an optical axis of the X-rays emitted from the X-ray emitter, forms a diffraction ring that is an image of the diffracted light of the X-rays on the imaging surface, and detects the diffraction ring; and a residual stress calculation means that calculates a residual stress of the measurement object based on data of the diffraction ring detected by the diffraction ring formation detection means, comprising correction calculation means for calculating information on a positional relationship between the optical axis of the X-rays for use by the residual stress calculation means and the imaging surface, wherein the diffraction ring formation detection means detects a first diffraction ring of a first sample with a known diffraction angle in advance and detects a second diffraction ring of a second sample with a known diffraction angle that is different from that of the first sample in advance, wherein the correction calculation means includes sample diffraction ring centroid position coordinate calculation means for obtaining centroid position coordinates of the first diffraction ring and centroid position coordinates of the second diffraction ring, X-ray optical axis inclination calculation means for obtaining an X-ray optical axis inclination that is an inclination of the optical axis of the X-rays with respect to the imaging surface from the centroid position coordinates of the diffraction ring of the first sample and the centroid position coordinates of the diffraction ring of the second sample, and X-ray emission point coordinate calculation means for obtaining X-ray emission point coordinates of the imaging surface when the distances to the imaging surface, the first sample, and the second sample are zero, wherein the residual stress calculation means corrects centroid coordinates of the diffraction ring of the measurement object detected by the diffraction ring formation detection means based on the X-ray optical axis inclination and the X-ray emission point coordinates of the imaging surface calculated by the correction calculation means, and calculates the residual stress of the measurement object. The X-ray diffractometer is characterized by this.

2. The residual stress calculation means obtains provisional centroid coordinates and an average radius of the diffraction ring of the measurement object detected by the diffraction ring formation detection means, obtains a centroid coordinate shift when there is no X-ray optical axis inclination based on a known diffraction angle when there is no residual stress in the measurement object, adds the centroid coordinate shift to the X-ray emission point coordinates to obtain corrected centroid coordinates, sets the corrected centroid coordinates as the origin and obtains corrected diffraction angles for the entire circumference of the diffraction ring, and calculates the residual stress of the measurement object from the corrected diffraction angles. The X-ray diffractometer according to Claim 1 is characterized by this.

3. The X-ray diffraction measurement apparatus according to claim 1 or claim 2, wherein the residual stress calculating means calculates the residual stress using the cosα method.

4. In a method for calculating residual stress of an X-ray diffraction measurement apparatus that irradiates an object to be measured with X-rays from an X-ray emitter that emits X-rays toward the object to be measured, receives diffracted light of the X-rays generated by the object to be measured on an imaging surface that intersects substantially perpendicularly to the optical axis of the X-rays emitted from the X-ray emitter, forms a diffraction ring that is an image of the diffracted light of the X-rays on the imaging surface, detects the diffraction ring, and calculates the residual stress of the object to be measured based on the data of the detected diffraction ring, detect a first diffraction ring of a first sample with a known diffraction angle in advance, and detect a second diffraction ring of a second sample with a known diffraction angle that is different from that of the first sample in advance, obtain the centroid position coordinates of the first diffraction ring and obtain the centroid position coordinates of the second diffraction ring, obtain the X-ray optical axis inclination, which is the inclination of the optical axis of the X-rays with respect to the imaging surface, from the centroid position coordinates of the diffraction ring of the first sample and the centroid position coordinates of the diffraction ring of the second sample, obtain the X-ray emission point coordinates of the imaging surface when the distances from the imaging surface to the first sample and the second sample are zero, based on the calculated X-ray optical axis inclination and the X-ray emission point coordinates of the imaging surface, detect the diffraction ring of the object to be measured, correct the centroid coordinates of the detected diffraction ring of the object to be measured, and calculate the residual stress of the object to be measured, which is a method for calculating residual stress by an X-ray diffraction measurement apparatus.

5. Obtain the provisional centroid coordinates and the average radius of the diffraction ring of the detected object to be measured, based on a known diffraction angle when there is no residual stress in the object to be measured, obtain the centroid coordinate deviation when there is no X-ray optical axis inclination from the provisional centroid coordinates, add the centroid coordinate deviation to the X-ray emission point coordinates to obtain corrected centroid coordinates, re-align the corrected centroid coordinates as the origin to obtain the corrected diffraction angle for the entire circumference of the diffraction ring, and calculate the residual stress of the object to be measured from the corrected diffraction angle, which is a method for calculating residual stress by the X-ray diffraction measurement apparatus according to claim 4.

6. A method for calculating residual stress by an X-ray diffraction measurement apparatus according to claim 4 or claim 5, wherein the residual stress is calculated using the cosα method.

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